Frankie has a brother who is two years older, 40 pounds heavier and has never spoken a meaningful word to him. At night, Dominic plays songs from Sesame Street so loud that Frankie sleeps with a pillow over his head to drown out the clamoring voices. Somebody come and play. Somebody come and play today.

“I wish Dominic would just wear headphones, Ma,” he mutters at the breakfast table.

I’ve begged Dominic to try, placing the ear buds gently in his ears, pleading with him to just listen. But he hates the weight, feel and loudness of them. He takes them off, every time.

Frankie shrugs and goes on, drifting off to fitful sleep each night against the soundtrack of his older brother’s disability. It’s not fair, of course, but what is? There is no arguing over fairness when you are the brother of a boy who cannot talk.

That, of course, is also not fair. But that is also nothing new to Frankie.

Frankie and Dominic have shared a room since they were born, 19 months apart. And from the start, the differences between them were palpable. While I watched my new baby, the one with the discerning blue eyes and long, thin limbs, hit every milestone on time, I shuffled his older brother to doctors, trying to piece together a diagnosis for some mysterious disease that had consumed him.

“He doesn’t talk. He never smiles. He won’t play,” I whispered to the neurologist. We watched my toddler flip through pages of “Goodnight Moon” with a smacking, ritual precision. When the doctor finally — tentatively — mentioned autism, I felt relief. Finally, a name for what haunted us.

As they grew, I watched the younger brother scramble past the older one at every turn. I did not have to tell Frankie about his brother’s disability; it was a constant stranger in even his earliest memory. He did not ask me why Dominic did not talk, but instead learned to communicate with him in other ways. Touch and music. Patience and acceptance.

This was the brother he was given. And when this is all you know, you do not understand what you are missing.

*

I worry about how my older son’s autism will affect his little brother. Our brothers and sisters are our first best friends, our first sworn enemies. From the moment we are born, those of us with siblings have a built-in social network, in the middle of the family room floor. These are the people who understand us, and as we go away from home and come back again, there is comfort in how well they know our limitations.

This is a wonderful trait. Except when it isn’t: Kids with siblings on the autism spectrum often put themselves last, even if that means sacrificing their needs for those of their sibling. As a parent, this is sobering and terrifying. And it poses a challenge that keeps me awake at night. Am I doing enough to make things fair? How can I carve out a separate space for my neurotypical son when he shares his room, his time, his entire world, with a severely disabled brother?

*

Courtesy of Nicole Jankowski

I sit in the car, at the top of the big sledding hill, near the center of town. Dominic sits beside me; we watch Frankie and all the other boys from the neighborhood whiz down the frozen incline.

“Sled,” he says, suddenly, his word a wild, gravelly sound.

“Sled?” I ask him, surprised. “You want to sled? You want to go down the hill?” He has on only a hat, coat and boots. No snow pants or gloves. “You’ll be cold, son. It’s cold.”

“Sled,” Dominic demands. I guide him to the top of the hill.

I watch my 13-year-old boy, with the shoulders of a man, fit himself into a child-sized blue sled. The other children dodge his errant descent as he zooms down the hill. At the bottom, Dominic stands up cautiously. He turns and faces the hill, letting the plastic sled drift into a snowbank. He stands there, flapping his arms in the air. I begin to panic.

But before I can race down the snow bank, I watch Frankie lean down to pick up the sled. Up the steep hill, Frankie carries his sled and Dominic’s, as his older brother follows close behind. Over Frankie’s shoulder, I see Dominic’s arms making giant circles in the cold air. Other children stop to watch them.

I watch him trudge up the slope: a little boy in his brother’s hand-me-down boots hoisting two sleds in his thin, long arms. I realize this is not the first time he has had to carry all the weight for them both. And I turn my head when the boys get to the car, so they do not see that I am crying.

*

Two nights later, I stop in their room before bed.

“Listen,” I say to Frankie, and I turn to his brother.

“Goodnight, Dominic,” I say. He has covered himself with his Thomas the Train comforter. On the laptop by his bed, he has cued up the Sesame Street album, the cursor hovering over the fourth track. Somebody come and play.

“Goodnight, Dominic,” I say again, anxiously. We have been practicing a new skill, answering and using names, for days. Dominic screws up his face, thinking hard. It looks so hard for him just to speak.

“Goodnight, Mommy.”

Frankie’s eyes open wide. He sits up and turns to his brother.

“Goodnight, Dominic,” Frankie calls, loudly.

Nothing.

He tries again. “Goodnight, Dominic.” He is almost shouting now.

Dominic looks at me. His face is soft and rounded in the darkness, lit up by the laptop screen. I beg him, silently, to give his brother just this one thing.

One more time, Frankie tries. “Goodnight, Dominic.” There is a pleading in his voice.

“Goodnight, Frankie.”

And, grateful, this is how I leave them. Two boys born two years apart, existing in the same four-walled space but orbiting very separate spheres.

The weight of disability is heavy, for the entire family. But the mysterious struggle of living with autism, existing in a world that doesn’t understand you, is much greater. Sharing a room with autism is difficult, but having autism in your brain? That makes everyday tasks like wearing headphones, sledding down a snowy hill, even talking, so much harder. This is something the kid brother of a boy with autism knows. Good or bad, fair or unfair, Frankie simply shoulders the substantial obligation that comes with dividing his world — and his room — with a disabled brother.

Such are the complicated burdens of biology and proximity and acceptance and family. Such are the invisible and cumbersome ties that bind. But that is why Frankie will always carry two sleds up the frozen hill. Because compared with the luckless, random, necessary weight of love, a sled doesn’t seem very heavy at all.

Jankowski is a mom of four kids and two awesome stepkids, a divorcée and a writer. Read about her experiences with autism, addiction and awesomeness at www.momof4istired.com or on Facebook and Twitter.